This is a proposal to determine the effects of zinc and cadmium exposure on delta amino-levulinic acid dehydrase (ALAD) activity, delta amino-levulinic acid (ALAU) excretion and free erythrocyte porphyrin (FEP) concentration in lead intoxicated rats. Lead will be administered orally while zinc and cadmium will be administered either orally or subcutaneously at levels appropriate to exposure in a heavy metal contaminated environment. Data will be analyzed to determine whether either lead-zinc or lead-cadmium interactions occur involving any of the 3 above lead exposure screening parameters. Blood lead, zinc and cadmium concentrations, and basic hematological readings will also be made. The basic objectives for this proposal is to clarify the effects of the interactions between lead and zinc, and lead and cadmium on 3 screening parameters for lead exposure. Since environments contaminated with lead are commonly contaminated with zinc and cadmium also an urgency exists for this work to be carried out to ensure the screening tests currently employed for testing lead exposure are not recording false negative results in lead intoxicated individuals exposed simultaneously to high levels of zinc or cadmium.